Media delivery today is done either by preloading a media file to local cache and then giving the user access to the contents of the file or, alternately, using streaming technology. In streaming technology, a media file is delivered in real time. Advantages of preloading include that there is no real time requirement as is needed for streaming and one can avoid unpredictable playback defects due to unpredictable congestion on the network. Disadvantages of preloading include the likely probability that a stored media file may not be secure and the possibility of unauthorized playback or copying of the stored media file may occur. In addition, the content of the media file delivered has only coarse control when accessed or played back. For example, the deliverer or copyright owner of the media file may impose a time limit for authorized access or playback of the stored media file. Additionally, the deliverer or copyright owner would not normally know exactly how much time was actually spent by the user accessing or playing back the media file. Furthermore, the deliverer or copyright owner would not normally know precisely when access or playback of the media would have occurred and at what time such access or playback actually occurred. Playback information would typically be available only in broadcast mode in the prior art, since the deliverer or copyright owner would know exactly when each segment of the media file was broadcast, to whom it was broadcast, and to whom it would have been received by or delivered to.
Advantages with prior art broadcast mode streaming techniques are similar to the advantages with on-demand or multicasting on the internet. The deliverer or copyright owner will know exactly when every portion of the media is delivered. Disadvantages of broadcast mode streaming, on-demand or multicasting, are that the bandwidth requirements are typically significant, many users with differing receiving equipment are typically participating, and many of the receiving users may request diverse media file contents. Streaming does have the advantage, however, that one receives media only as desired.
What is needed is the ability to deliver a media file to a cache which is local to a user, but which is not accessible by the user until the media file deliverer or copyright owner authorizes access to or playback of the media file.